The potential of unmanned aerial systems for sea turtle research and conservation: a review and future directions

Alan F Rees ,Elizabeth Whitman ,Miguel R Varela ,Larisa Avens ,Annette C Broderick ,Michael R Heithaus ,Kellie Pendoley ,Katia Ballorain ,Richard D Reina ,Nathan J Robinson ,Dominic Tilley ,Paul A Whittock ,Thane Wibbels ,Gwénaël Duclos ,David W Johnston ,Seth T Sykora‐Bodie ,Elizabeth Bevan ,Jeffrey C Mangel ,Frank V Paladino ,Robert Ryan ,Raymond R Carthy ,Marjolijn J A Christianen ,Brendan J Godley

doi:10.3354/esr00877

Abstract

The use of satellite systems and manned aircraft surveys for remote data collection has been shown to be transformative for sea turtle conservation and research by enabling the collection of data on turtles and their habitats over larger areas than can be achieved by surveys on foot or by boat. Unmanned aerial vehicles (UAVs) or drones are increasingly being adopted to gather data, at previously unprecedented spatial and temporal resolutions in diverse geographic locations. This easily accessible, low-cost tool is improving existing research methods and enabling novel approaches in marine turtle ecology and conservation. Here we review the diverse ways in which incorporating inexpensive UAVs may reduce costs and field time while improving safety and data quality and quantity over existing methods for studies on turtle nesting, at-sea distribution and behaviour surveys, as well as expanding into new avenues such as surveillance against illegal take. Furthermore, we highlight the impact that high-quality aerial imagery captured by UAVs can have for public outreach and engagement. This technology does not come without challenges. We discuss the potential constraints of these systems within the ethical and legal frameworks which researchers must operate and the difficulties that can result with regard to storage and analysis of large amounts of imagery. We then suggest areas where technological development could further expand the utility of UAVs as data-gathering tools; for example, functioning as downloading nodes for data collected by sensors placed on turtles. Development of methods for the use of UAVs in sea turtle research will serve as case studies for use with other marine and terrestrial taxa.

Highlights

Remote sensing data are becoming increasingly important for understanding the spatial ecology of marine systems and, when used in tandem with tracking data, can provide important insights into the specific environmental niches and spatial distribution of target species
Unmanned aerial vehicles (UAVs) are helping revolutionise the field of spatial ecology (Anderson & Gaston 2013), and are proving useful for studying biodiversity and habitats that are difficult or dangerous to access from the ground (Chabot & Bird 2015)
Sea turtle researchers and managers need to ensure they are correctly equipped to maximise the usefulness of results and draw benefits from new data acquisition capabilities facilitated by use of UAVs

Summary

INTRODUCTION

Remote sensing data are becoming increasingly important for understanding the spatial ecology of marine systems and, when used in tandem with tracking data, can provide important insights into the specific environmental niches and spatial distribution of target species (fish: Druon et al 2016; sea turtles: Thums et al 2017; sea birds: Afán et al 2014; seals: Nachtsheim et al 2017; cetaceans: do Amaral et al 2015). This method could be used to generate nesting turtle counts on established nesting beaches where access to the beach is logistically demanding or dangerous, or where high nesting densities make ground surveys difficult Turtles identified by their heat signatures are tallied manually by one or more researchers, either during the UAV flight in near real-time, from video replay at a later date, or through machine learning techniques, such as image and pattern recognition. Adult (vs juvenile) male and female turtles can be readily manually differentiated in high-resolution UAV footage recorded at a suitable altitude, as the tail of adult males extends well past the rear of the carapace (Bevan et al 2016) (Fig. 4) This manual method has been successfully used to determine OSR by calculating the sex ratio of individuals from images recorded during transects (Schofield et al 2017a); this assumes that males and females have an equal chance of being observed and correctly identified, and this potential bias would need to be addressed in the survey design. 2017) include (1) behaviour and movements of turtles in clear, shallow water habitats (https://vimeo.com/ 175689526; >16 000 views) or on a nesting beach (https://youtu.be/RPxPIxN2VpQ; >9800 views); (2) release of a turtle back to the sea after human intervention, e.g. rescue after illegal capture, attachment of a satellite transmitter, post-rehabilitation release etc. (e.g. https://youtu.be/i3LQYV7_aD8 >10 000 views); (3) field researchers working, either with turtles in a boat or with a nest on a beach; (4) flights over daytime nesting events — especially arribadas (mass nesting events where several hundred to several thousand turtles come ashore to nest at once) (https:// youtu.be/mY29SN y0Y9Y >44000 views; note this is footage from a microlight aircraft and similar UAV footage should be of better quality); and (5) footage of a turtle rescue/rehabilitation centre showing turtles in pools (e.g. https://vimeo.com/204257624)

DISCUSSION

CONCLUSIONS